Multi-stage hydrocracking process



Aug. 16, 1966 G. D. GOULD MULTI-STAGE HYDROCRACKING PROCESS Filed March30, 1964 GEORGE D. GOULD BY A ,l I

ATTORNEYS United States Patent Office Patented August 16, 1956 3,267,021MULTI-STAGE HYDROCRACKING PROCESS George D. Gould, Orinda, Calif.,assigner to Chevron Research Company, a corporation of Delaware FiledMar. 30, 1964, Ser. No. 355,653 2 Claims. (Cl. 208-78) This inventionrelates to a hydrocarbon conversion process, more particularly to ahydrocarbon conversion process for converting hydrocarbon feeds,including petroleum distillate and residuum feeds, into various valuableproducts, and still more particularly to a catalytic conversion processcapable of producing middle distillates and gasoline from said feeds.

It yis well known that nitrogen in a hydrocarbon feed is deleterious tocertain hydrocracking catalysts, particularly highly acidichydrocracking catalysts, and that in order to provide a practicalprocess for producing gasoline over a highly acidic hydrocrackingcatalyst from a feed containing substantial amounts of nitrogen, it Iisgenerally necessary to first hydrofne the feed to remove substantiallyall of the nitrogen. It is also well known that such highly acidiccatalysts do not result in the production of substantial quantities ofmiddle distillates and that where gasoline production and alsosubstantial middle distillate production is desired a catalyst having nomore than weak acidity is desirable. While it is possible to meet theaforesaid problems by operating a two-stage process wherein thehydrofining-hydrocracking catalyst having no more than weak acidity isused in the first stage and an acidic hydrocracking catalyst is used inthe second stage, such a process still has undesirable aspects.Operation of the first stage at hydrolining conditions severe enough toreduce the nitrogen content of the feed to an acceptably low level,particularly where maximum middle distillate production is desired,frequently results in a greater amount of hydrocracking, gasoline andlight gas production and catalyst fouling in the first stage than isdesired. On the other hand, operation of the first stage at less severeconditions which do not result in an excessive amount of hydrocrackingfrequently leaves a greater concentration of nitrogen in the eiiiuentfrom the first stage than can be tolerated for sustained periods by theacidic catalysts in the second stage.

In View of the foregoing, it is an object of the present invention toprovide a multi-stage process for converting raw feeds, includingnitrogen-containing feeds, to gasoline and middle distillates whereinselected portions of said feeds are hydrocracked and partiallyhydrofined in each stage with catalysts having no more than weak acidityt produce middle distillate products and higher boiling materials andwherein selected portions of said higher boiling materials arehydrocracked in the same catalyst system in a manner which results in amaximum over-al1 production of middle distillates, at minimum cost,without excessive catalyst fouling in any stage.

The invention will best be understood, and further objects andadvantages thereof will be apparent, from the following description whenread in conjunction with the accompanying drawing which is adiagrammatic illustration of process units and flow paths suitable forcarrying out the process of the present invention.

In accordance with one embodiment of the present invention there isprovided a process for producing gasoline and middle distillates from ahydrocarbon feed selected from the group consisting of petroleumdistillates and petroleum residua boiling `above 500 F., which comprisesselecting at least two feed fractions boiling above 500 F. and havingdifferent boiling ranges, hydrocracking the lighter of said fractions inthe presence of from 1,000 to 10,000 s.c.f. of hydrogen per -barrelthereof in a first conversion zone at a temperature from 500 to 950 F.,a pressure above 500 p.s.i.g. and an LHSV of 0.1 to 4.0 with a catalysthaving no more than weak acidity comprising at least one hydrogenatingcomponent selected from the Group VI metals and compounds of Group VImetals and at least one hydrogenating component selected from the GroupVIII metals land compounds of Group VIII metals in intimate association'with a silica-containing support, hydrocracking the heavier of saidfractions in a second conversion zone under conditions within theaforesaid ranges with a catalyst having the aforesaid description,.recovering from each of said zones lat least one prodtuct boiling belowthe initial lboiling point of the feed to said zone, and passing heaviermaterials from each zone to said second zone only.

In accordance with a more specific embodiment of the present invention,there is provided a process for producing gasoline and middledistillates from a hydrocarbon feed selected from the group consistingof petroleum distillates and petroleum residua boiling above 650 F.which comprises separating said feed into a first fraction and a secondfraction of different boiling range, hydrocracking said first fractionin the presence of from 1000 to 10,000 s.c.f. of hydrogen per 4barrelthereof in a first conversion zone at a temperature of from 500 to 950F., ya pressure above 500 p.s.i.g., and an LHSV of from 0.1 t0 4.0 witha catalyst having no more than weak acidity comprising at least onehydrogenating -component selected from the Group VI metals and compoundsof Group VI metals and at least one hydrogenating component selectedfrom the Group VIII metals and compounds of Group VIII metals inintimate lassociation with a silica-containing support, recovering atleast one product boiling Ibelow 550 F. from said first conversion zone,hydrocracking said second fraction in the presence of from 1000 to 10,-000 s.c.f. of hydrogen per barrel thereof in a second conversion zone ata temperature of from 500 to 950 F., a pressure. above 500 p.'s.i.g.,and an LHSV of from 0.1 to 4.0 with a catalyst having no more than weakacidity comprising at least one hydrogenating component selected fromhte Group VI metals and compounds of Group VI metals and at least onehydrogenating component selected from the Group VIII metals andcompounds of Group VIII metals in intimate association with asilicacontaining support, recovering at least one product boiling below550 F. from said second conversion zone, 'and passing to said secondconversion zone from each of said first and second conversion zones afraction boiling above 550 F.

Suitable feeds for use in the process of the present invention arepetroleum distillates, including nitrogencontaining petroleumdistillates, and petroleum residua, including nitrogen-containingpetroleum residua, from which fractions can be selected boiling above500 F., preferably fractions boiling between 500,a F. and 1200 F., andmixtures of the foregoing. Heavy gas oils and catalytic cycle oils areexcellent feeds to the process, as well as conventional FCC feeds andportions thereof. Residual feeds may include Minas and otherparainictype residua as well as solvent decarbonized oils from a widerange of residua. Other suitable4 feeds include tar sand oils, shaleoils and coal tar distillates.

The aforesaid catalysts having-no more than Weak acidity comprise atleast one hydrogenating component selected from the Group VI metals andcompounds of the Group VI metals and at least one hydrogenatingcomponent selected from the Group VIII metals and com* pounds of GroupVIII metals. Preferred combinations of hydrogenating components includenickel sulfide and tungsten sulfide, nickel sulfide and molybdenumsulfide, and palladium sulfide and molybdenum sulfide.

The aforesaid catalysts having no more than weak acidity comprise asupport, preferably one that is moderately acidic, but not more thanmoderately acidic, as compared with highly acidic supports such assilicaalumina. Said support preferably is selected from the groupconsisting of silica-magnesia supports, silicaalumina supportscontaining less than 70 weight percent of silica, andsilica-alumina-magnesia supports having a silica content less than 80weight percent.

The aforesaid catalysts having no more than weak acidity are relativelynitrogen-insensitive compared with conventional acidic hydrocrackingcatalysts such as nickel sulfide on silica-alumina. Accordingly, thenitrogen content of the feed used in the process of the presentinvention may be relatively high and excellent hydrocracking resultsstill may be obtained in the conversion zones containing said catalystsat reasonable temperatures without the necesssity for rapidly raisingthe temperature to maintain conversion as is necessary whenhydrocracking a high nitrogen content feed of a conventional acidichydrocracking catalyst, such as nickel sulfide on silicaalumina. Thenitrogen content of the feed in the present process may range from lessthan parts per million to 30,000 parts per million. The process isespecially attractive for processing heavy feed containing at least 500parts per million nitrogen.

Although high nitrogen content feeds can be tolerated by said catalystshaving no more than weak acidity, it will be noted that said catalystsalso are excellent hydrodenitrification catalysts and are efficient inconcurrently hydrofining as well as in hydrocracking the feed.Nevertheless, the process of the present invention may be rendered evenmore efficient if very high nitrogen content feeds are rst hydrofined byconventional methods to at least somewhat reduce their nitrogen contentbefore hydrocracking them in the presence of said catalysts having nomore than weak acidity in accordance with the present invention.

Conversion zones in the process of the present invention containing saidcatalysts having no more than weak acidity are operated at combinationsof conditions selected from within the following ranges that willproduce the desired degree of hydrocracking: a temperature of about 500to 950 F., preferably 650 to 850 F.; a hydrogen partial pressure of 500to 3500 p.s.i.g., preferably 1000 to 2500 p.s.i.g.; and an LHSV of fromabout 0.1 to 4.0, preferably 0.4 to 2.0. The hydrogen flow to saidconversion zones may be from 1000 to 12,000 s.c.f. per barrel of feed,and preferably 2500 to 8000 s.c.f. per barrel of feed. The higherhydrogen partial pressures, particularly with unrened feeds, give lowercatalyst fouling rates, and therefore, for longer catalyst lives, it ispreferable to operate above 2000 p.s.i.g. total pressure and above 1000p.s.i.g. hydrogen partial pressure.

Referring now to the drawing, there shown is an exemplary diagrammaticillustration of an embodiment of process units and flow paths suitablefor carrying out the process of the present invention.

A hydrocarbon feed which may be, and in this example is, a petroleumdistillate feed containing materials boiling about 650 F., is passedthrough line 1 to distillation column 2, where it is separated intovarious fractions as shown. A gaseous fraction is removed from column 2through line 3, a C5-650 IF. fraction is removed through line 4, and, ifdesired, a residuum fraction boiling above 110 F. is removed throughline 5. A 650 to 900 F. fraction is passed from separation zone 2through line 6 into contact in hydrocracking zone 7 with the aforesaidhydrocracking catalyst having no more than weak acidity and withhydrogen entering zone 7 through line 8 under the hydrocrackingconditions previously discussed, at a per-pass conversion preferablyabove about 40%. From zone 7, an efuent is passed through line 9 toseparation zone 10, from which hydrogen is recycled through line 15,ammonia is Withdrawn through line 16, and remaining materials are passedthrough line 17 to separation zone 18. From separation zone 18 productstreams boiling below about 400 F., and from about 400 to 650 F.,respectively, are withdrawn through lines 19 and 25, respectively. Fromseparation zone 1S, materials boiling above about 650 F. are passed tohydrocracking zone 31, discussed below. If desired a portion of thematerials in line 20 may be withdrawn through line 26 and passed to acatalytic cracking zone, or withdrawn completely from the system, orused for any other desired purpose, for example as a lube oil stock.

A 900 to 1l00 F. fraction, together with materials in line 20, is passed.from separation zone 2 through line 30 into |contact in hydrocrackinigzone 31 with the aforesaid hydrocrackinig catalyst having no more thanweak acidity and with hydrogen entering zone 31 through line 32 underthe hydrocracking conditions previously discussed, at a per-passconversion preferably above about 40%. From zone 31 an efuent is passedthrough line .33 to separation zone 34 from which hydrogen is recycledthrough line 35 to zone 31, ammonia is Withdrawn through line 36, `andremaining materials are passed through line 37 to separation zone 38.From separation zone 38, products boiling below about 400 F., and from400 to 650 F., respectively, are recovered through lines 39 and 46,respectively, and materials boiling above about 650 F. are returned tozone 31 through lline 40. A portion of the materials in line 40 may bepassed through line 45 to a catalytic cracking zone, or removedcompletely from the system, or used for any other desired purpose, forexample as a lube stock.

From the foregoing, it wifll be seen that the process of the presentinvention, wherein the first lhydrocracking zone is operated on aonce-through basis and the second hydrocracking zone is operated on arecycle basis, is effective in producing middle distillates in goodyields.

Although only specific embodiments of the present invention have beendescribed, numerous variations can be made yof those embodiments withoutdeparting from the spirit of the invention, and all such variations thatfall within the scope of the appended claims yare intended to beembraced thereby.

I claim:

1. A process for producing gasoline and middle distillates from ahydrocarbon feed boiling above 500 F. which comprises selecting at leasttwo feed fractions boiling above 500 F. and having different boilingranges catalyti-callly hydrocracking the lighter of said fractions inthe presence of from 1000 to 12,000 s.c.f. of hydrogen per barrelthereof in a first lconversion zone at ya temperature from 500 to 950F., a pressure above 500 p.s.i.g. `and an LHSV of from 0.1 to 4.0 with acatalyst comprising at 'least one hydrogenating component selected fromthe Group VI metals and compounds of Group VI metals and at least onehydrogenating component selected from the Group VIII Imetals andcompounds of Group VIII metals in intimate association with 'a supportselected from the group consisting of silica-magnesia supports,silica-allumina supports containing less than 70 weight percent lofsilica, and silica-alumirra-imfaignesia supports having a silica contentless than 8O weight percent, catalyticallly hydrocracking the heavier ofsaid fractions in a second conversion zone under conditions within theyaforesaid ranges with 1a catalyst having the aforesaid description,said heavier fraction being passed through the catalyst body in said.second conversion zone, recovering from eaoh of said zones at least oneproduct boiling below the initial boiling point of the feed to saidzone, including substantially all gasoline boiling below 400 F. producedin said zone, and passing heavier materials from each Zone to saidsecond zone onily.

2. A process for producing gasoline and middle distillates from ahydrocarbon ifeed selected `fro-m the group consisting of petroleumdistillates and petr-oleum residua boiling above 650 F., whichlcomprises separating said feed into -a first fraction and a generallyheavier second fraction of different boiling range, lcatalyticalyhydrocracking said rst fraction in the presence of from 1000 to 12,000s.c.f. of hydrogen per barrel thereof in a first conversion zone at atemperature from 500 to 950 F., a pressure above 500 p.s.i.g, and anLHSV of from 0.1 `to 4.0 with :a catalyst `comprising at least onehydrogenating component selected from the Group VI metals and lcompoundsof Group VI metals and at least one hydrogenating component selectedffrom the Group VIII metals and compounds of Group VIII metals inintimate iassociation with a support selected from the group consistingof silica-magnesia supports, silica-alumina supports containing lessthan 70 weight percent of silica, and silica- :alumina-magnesia supportshaving a silica content lless than 80 weight percent, yrecovering atleast one product boiling below 500 F. from said first conversion zone,including substantially all .gasoline boiling below 400 F. produced insaid zone, catalytic-ally hydrocracking said second fraction in thepresence of from 1000 to 12,000 s.c.f. of hydrogen per barrel thereof ina second conversion zone :at a temperature from 500 to 950 F., apressure above 500 p.s.i.g., and an LHSV of yfrom 0.1 to 4.0 with acatalyst comprising at least one hydrogenating component selected fromthe Group VI metals and compounds of Group VI metals and at least onehydrogenating component selected from the Group VIII metals andcompounds of Group VIII metals in intimate association with ya supportselected from the group consisting of silica-magnesia supports,silica-alumina supports containing less than weight percent of silica,and silicaalumina-magnesia supports having a silica content less thanWeight percent, said generailly heavier fraction 'being passed throughthe catalyst body in said second conversion zone, recovering at leastone product boiling below 550 F. from said second conversion zone, andpassing to said second conversion zone -from said each of said first andsecond conversion zones a fraction boiling above 550 F.

References Cited by the Examiner UNITED STATES PATENTS 3/1965 Claussenet -al 208-111 3/1965 Burch 208-111

1. A PROCESS FOR PRODUCING GASOLINE AND MIDDLE DISTILLATES FROM AHYDROCARBON FEED BOILING ABOVE 500*F. WHICH COMPRISES SELECTING AT LEASTTWO FEED FRACTIONS BOILING ABOVE 500*F. AND HAVING DIFFERENT BOILINGRANGES CATALYTICALLY HYDROCRACKIMG THE LIGHTER OF SAID FRACTIONS IN THEPRESENCE OF FROM 100 TO 12,000 S.C.F. OF HYDROGEN PER BARREL THEREOF INA FIRST CONVERSION ZONE AT A TEMPERATURE FROM 500*TO 950*F., A PRESSUREABOVE 500 P.S.I.G. AND AN LHSV OF FROM 0.1 TO 4.0 WITH A CATALYSTCOMPRISING AT LEAST ONR HYDROGENATING COMPONENT SELECTED FROM THE GROUPVI METALS AND COMPOUNDS OF GROUP VI METALS AND AT LEAST ONEHYDROGENATING COMPONENT SELECTED FROM THE GROUP VIII METALS ANDCOMPOUNDS OF GROUP VIII METALS IN INTIMATE ASSOCIATION WITH A SUPPORTSELECTED FROM THE GROUP CONSISTING OF SILICA-MAGNESIA SUPPORTS,SILICA-ALUMINA SUPPORTS CONTAINING LESS THAN 70 WEIGHT PERCENT OFSILICA, AND SILICA-ALUMINA-MAGNESIA SUPPORTS HAVING A SILICA CONTENTLESS THAN 80 WEIGHT PERCENT, CATALYTICALLY HYDROCRACKING THE HEAVIER OFSAID FRACTIONS IN A SECOND CONVERSION ZONE UNDER CONDITIONS WITHIN THEAFORESAID RANGES WITH A CATALYST HAVING THE AFORESAID DESCRIPTION, SAIDHEAVIER FRACTION BEING PASSED THROUGH THE CATALYST BODY IN SAID SECONDCONVERSION ZONE, RECOVERING FROM EACH OF SAID ZONES AT LEAST ONE PRODUCTBOILING BELOW THE INITIAL BOILING POINT OF THE FEED TO SAID ZONE,INCLUDING SUBSTANTIALLY ALL GASOLINE BOILING BELOW 400*F. PRODUCED INSAID ZONE, AND PASSING HEAVIER MATERIALS FROM EACH ZONE TO SAID SECONDZONE ONLY.